Electrode material, paste for electrodes, and lithium ion battery

Abstract

An electrode material in which an electrode active material having a carbonaceous film formed on the surface is used, a migration path through which lithium ions diffuse is maintained in the carbonaceous film, and the lithium ion conductivity is also improved while the electron conductivity is supported by the carbonaceous film is provided. A electrode material, wherein the electrode material have a particulate shape, the electrode material is formed a carbonaceous film on surfaces of electrode active material particles, a coating proportion of the surfaces of the electrode active material particles by the carbonaceous film is 80% or more, and an apparent density (ρV) of the carbonaceous film calculated from an amount of carbon in the electrode material, a specific surface area of the electrode material, and an average film thickness of the carbonaceous film is in a range of 0.10 g/cm 3 to 1.08 g/cm 3 .

What is claimed is: 
     
       1. An electrode material, comprising:
 electrode active material particles and a carbonaceous film provided on surfaces of the electrode active material particles, wherein the electrode active material particles having the carbonaceous film provided thereon form an electrode material having a particulate shape; 
 wherein a proportion of the surfaces of the electrode active material particles coated by the carbonaceous film is 80% or more; and 
 wherein an apparent density ρV of the carbonaceous film is in a range of 0.10 g/cm 3  to 1.08 g/cm 3 , wherein the apparent density ρV of the carbonaceous film is calculated from an amount of carbon in the electrode material, a specific surface area of the electrode material, an average film thickness of the carbonaceous film, a proportion of a carbon component in a total mass of the electrode material is in a range of 0.6% by mass to 5.0% by mass, a true density ρT if the carbonaceous film obtained using a gas-phase substitution method is in a range of 1.80 g/cm 3  to 2.50 g/cm 3 , and a ratio ρV/ρT of the apparent density ρV of the carbonaceous file to the true density of the carbonaceous film is in a range of 0.04 to 0.60. 
 
     
     
       2. The electrode material according to  claim 1 ,
 wherein the proportion of the carbon component in a total mass of the carbonaceous film is 50% by mass or more. 
 
     
     
       3. The electrode material according to  claim 1 ,
 wherein the electrode active material particles include as a main component one selected from a group of lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, and Li x A y D z PO 4 , where A represents one or more selected from the group consisting of Co, Mn, Ni, Fe, Cu, and Cr, D represents one or more selected from the group consisting of Mg, Ca, S, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements, 0<x<2, 0<y<1.5, and 0<z<1.5. 
 
     
     
       4. The electrode material according to  claim 1 ,
 wherein an average particle diameter of the electrode active material particles is in a range of 10 nm to 20,000 nm. 
 
     
     
       5. The electrode material according to  claim 1 ,
 wherein the electrode active material particles have a spherical shape. 
 
     
     
       6. The electrode material according to  claim 1 ,
 wherein the electrode active material particles having the carbonaceous film provided thereon form an agglomerate in a state in which the electrode active material particles having the carbonaceous film provided thereon agglomerate together in a point contact state. 
 
     
     
       7. The electrode material according to  claim 6 ,
 wherein an average particle diameter of the agglomerate is in a range of 0.5 μm to 100.0 μm. 
 
     
     
       8. The electrode material according to  claim 6 ,
 wherein a volume density of the agglomerate is in a range of 50% by volume to 80% by volume of a volume density of a solid agglomerate having no space therein and the density of which is equal to a theoretical density of the electrode active material. 
 
     
     
       9. The electrode material according to  claim 6 ,
 wherein a volume density of the agglomerate is in a range of 55% by volume to 75% by volume of a volume density of a solid agglomerate having no space therein and the density of which is equal to a theoretical density of the electrode active material. 
 
     
     
       10. The electrode material according to  claim 6 ,
 wherein a volume density of the agglomerate is in a range of 60% by volume to 75% by volume of a volume density of a solid agglomerate having no space therein and the density of which is equal to a theoretical density of the electrode active material. 
 
     
     
       11. The electrode material according to  claim 1 ,
 wherein the proportion of the surfaces of the electrode active material particles coated by the carbonaceous film is 85% or more. 
 
     
     
       12. The electrode material according to  claim 1 ,
 wherein the proportion of the surfaces of the electrode active material particles coated by the carbonaceous film is 90% or more. 
 
     
     
       13. The electrode material according to  claim 1 ,
 wherein the apparent density ρV of the carbonaceous film is in a range of 0.15 g/cm 3  to 0.80 g/cm 3 , wherein the apparent density ρV of the carbonaceous film is calculated from an amount of carbon in the electrode material, a specific surface area of the electrode material, and an average film thickness of the carbonaceous film. 
 
     
     
       14. The electrode material according to  claim 1 ,
 wherein the apparent density ρV of the carbonaceous film is in a range of 0.20 g/cm 3  to 0.60 g/cm 3 , wherein the apparent density ρV of the carbonaceous film is calculated from an amount of carbon in the electrode material, a specific surface area of the electrode material, and an average film thickness of the carbonaceous film. 
 
     
     
       15. The electrode material according to  claim 1 ,
 wherein a proportion of a carbon component in a total mass of the electrode material is in a range of 0.7% by mass to 4.0% by mass, a true density ρT of the carbonaceous film obtained using a gas-phase substitution method is in a range of 1.85 g/cm 3  to 2.35 g/cm 3 , and a ratio ρV/ρT of the apparent density ρV of the carbonaceous film to the true density of the carbonaceous film is in a range of 0.08 to 0.50. 
 
     
     
       16. The electrode material according to  claim 1 ,
 wherein a proportion of a carbon component in a total mass of the electrode material is in a range of 0.8% by mass to 2.5% by mass, a true density ρT of the carbonaceous film obtained using a gas-phase substitution method is in a range of 1.90 g/cm 3  to 2.20 g/cm 3 , and a ratio ρV/ρT of the apparent density ρV of the carbonaceous film to the true density of the carbonaceous film is in a range of 0.12 to 0.40. 
 
     
     
       17. The electrode material according to  claim 1 ,
 wherein an average film thickness of the carbonaceous film is in a range of 0.5 nm to 20 nm. 
 
     
     
       18. A paste for electrodes comprising:
 the electrode material according to  claim 1 ; and 
 a binding agent. 
 
     
     
       19. A lithium ion battery comprising:
 a positive electrode current collector having an electrode material layer formed of the paste for electrodes according to  claim 18  on a metal foil.